A significant number of telephone calls go unanswered, with their intended purpose defeated, as a result of the called party's either being not available to answer or being busy on another call. Although a number of remedies for this problem have been proposed, for example, the use of answering service bureaus or private answering machines, or the implementation of customized call-waiting telephone service, these have not proven particularly satisfactory due to cost, inadequate response time, or general inconvenience.
Response to a callback request message received on a common answering machine recording, for instance, usually requires an intermediate transcription of the caller's number with subsequent individual entry of that number by the customer. More expensive and sophisticated answering machines, such as described by Klausner et al., U.S. Pat. No. 4,304,968, provide means for digitally recording a phone number input by an unanswered caller, to be later displayed or automatically dialed, at the option of the called party; however, such equipment is permanently affixed to a user's phone line and can only be utilized at the user's premises.
There has also been proposed an automatic callback service within the customer's local telephone switching system which would provide for the switch, upon the customer's requesting signal, to place a call to the memory-stored number of the party who had last called the customer's number. While this procedure eliminates some of the earlier-noted drawbacks of prior alternatives, it unfortunately introduces disadvantages of its own. Among these are the limitation of retained call identification to only the single most recent call, the lack of customer notification of the number that will be called by the system, and the lack of knowledge or consent on the part of the calling party with respect to retention of the number.
Each of the foregoing approaches requires, of course, that the called station be simply unattended, and not otherwise engaged as a busy line. Under the latter condition, call-waiting services provide some relief, but suffer from such undesirable aspects as persistent conversation interruption and lack of busy line awareness on the part of the calling party in the event of non-response by the called customer.
The need has thus long persisted for a system which can provide the called customer, and the calling party as well, with the ability, in the event of either an unattended or a previously engaged called phone station, to voluntarily implement options which will enable the completion of any number of calls which the customer was unable to answer over an extended span of time. The present invention now provides such a system.